Energy harvesting in {Λ-[Ru(bpy)3]Δ-[Os(bpy)3]}(PF6)4 and tunability of emission properties under magnetic field application

{Λ-[Ru(bpy)3]Δ-[Os(bpy)3]}(PF6)4 is the first representative of a new class of materials. The crystal structure is built up of homochiral layers of Λ-[Ru(bpy)3]2+ that alternate with homochiral layers of Δ-[Os(bpy)3]2+. At low temperature, the excitation energy is transferred efficiently by radiationless processes to one single crystallographic site of Δ-[Os(bpy)3]2+. Due to energy accumulation at this site of lowest energy, the new compound exhibits the interesting property of self-site-selectivity. Thus, one obtains highly resolved one-site emission spectra of Δ-[Os(bpy)3]2+ for every excitation wavelength. With application of a magnetic field, e.g., of B=12 T, the intensity of the lowest electronic 0–0 transition increases by several orders of magnitude and the vibrational satellite structure is changed from a vibronically induced (Herzberg–Teller) to a Franck–Condon induced structure. This is due to a magnetically induced coupling between lower lying triplet substates. Similar observations have not been reported yet for other compounds.